It also said it was now working with 62,000 families - but according to the NAO, this is 13% below the number it should be.

The NAO report added the DWP programme was "falling well short of its projections". None of the firms it contracted had met the department's goals, with only 720 people in jobs by September 2013 - less than 4% of targets.

Mark Serwotka, general secretary of the Public and Commercial Services union said "private companies are proving themselves incapable of providing the kind of complex, dedicated support necessary, despite the hundreds of millions of pounds of public money being funnelled their way".

However, the DWP said the NAO had only examined one area of its work and, in total, 2,400 members of troubled families had been helped into a job since its programme began.

Sir Bob Kerslake, Department for Communities and Local Government Permanent Secretary, added the employment side of the programmes was on an "upward curve", with 150 jobcentre advisers now specifically focusing on troubled families.

He said the DCLG scheme had made "substantial achievements that are changing lives for the better in multiple ways and bringing down the cost of troubled families to the taxpayer, so we are pleased with the progress so far with this innovative initiative".